Field of the Invention
One embodiment of the present invention relates to a lithium-ion storage battery and an electronic device.
Note that one embodiment of the present invention is not limited to the above technical field. The technical field of one embodiment of the invention disclosed in this specification and the like relates to an object, a method, or a manufacturing method. In addition, one embodiment of the present invention relates to a process, a machine, manufacture, or a composition of matter. Specifically, examples of the technical field of one embodiment of the present invention disclosed in this specification include a semiconductor device, a display device, a liquid crystal display device, a light-emitting device, a lighting device, a power storage device, a storage device, a method for driving any of them, and a method for manufacturing any of them.
Description of the Related Art
In recent years, a variety of power storage devices, for example, storage batteries such as lithium-ion storage batteries, lithium-ion capacitors, and air cells have been actively developed. In particular, demand for lithium-ion storage batteries with a high output and a high energy density has rapidly grown with the development of the semiconductor industry, for electronic devices, for example, portable information terminals such as mobile phones, smartphones, and laptop computers, portable music players, and digital cameras; medical equipment; next-generation clean energy vehicles such as hybrid electric vehicles (HEVs), electric vehicles (EVs), and plug-in hybrid electric vehicles (PHEVs); and the like. The lithium-ion storage batteries are essential as rechargeable energy supply sources for today's information society.
The performance required for the lithium-ion storage batteries includes increased energy density, improved cycle life, safe operation under a variety of environments, and longer-term reliability.
Furthermore, flexible display devices used while being mounted on human bodies or curved surfaces, such as display devices mounted on heads (head-mounted displays), have been proposed in recent years. This has increased demands for flexible storage batteries that can be mounted on curved surfaces to be used together with flexible display devices.
An example of the lithium-ion storage battery includes at least a positive electrode, a negative electrode, and an electrolyte solution (Patent Document 1).
Owing to excellent electric characteristics such as high conductivity or high mobility and excellent physical characteristics such as sufficient flexibility and high mechanical strength, application of graphene to a variety of products has been attempted recently (see Patent Documents 2 to 4).
Here, in a commercially available storage battery, which is a rechargeable power storage device, a carbon-based material such as graphite is used for a negative electrode. Graphite has a crystal structure where sheets of carbons which have sp2 hybrid orbitals and are regularly arranged two-dimensionally are stacked. The storage battery is charged and discharged utilizing occlusion of lithium ions from a positive electrode into a gap between sheets of carbons in the crystal structure.
Carbon-based materials are advantageous in achieving lighter storage batteries and are highly safe as materials, suggesting the necessity of the wider application of carbon-based materials to storage batteries.